Does anyone know if this limit has been cracked yet? If not is anyone working on it? Where would that limit be programmed in the ecm? I called TPIS, and they said, "we can program that computer to read a jet engine if we want." I assume that means they know what to change to break the 255 g/sec limit.

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82' Z-28. 327" w/ flat tops. 216/228/112LS. Pocket ported 041 heads 1.94/1.50 SS valves. World Class T-5 from a 91'. Best run? Runs with 2001 vette to 150mph! Soon to be converted over to TPI w/ supercharger.

 

It's the sensor and it's calibration.
Read a jet engine, ya ever notice some folks say anything to sell you something?..
There's more materail on this in the archives at DIY_EFI.

 

Actually, a Jet Engine would be simpler to program IMO. No valves, no timing...just keep adding fuel.

With the 165 MAF, I don't think there would be enough room to change the single byte table to a double byte table so it could handle a value greater than 255...and that is if you could get a MAF sensor that registers more than 255 gm/sec to work on the 165 MAF...which is the major problem.

Then there is the problem of double checking all the calculations in the eprom to make sure it doesn't overflow the 16 bit arithmetic register. The Motorolla HC11 is quite limited when it comes to 16 bit math. It is basically an 8 bit processor.

 

Actually, there is a way. Myself and another guy tried it and it works. It invloves using a ported MAF and rescaling the tables down 30% and reducing the injector constant by 30% and also icreasing the LV8 scalign factor by 30%. This will rough you in but required alot more work than I'm willing to do to get correct. On my 396, the MAF was not maxed out at 6300 rpm.

Jason

 

Yes, "fudging the system" is really the only way I can think of at this time as a "quick and dirty" around the code.

It is similar to using a 2 BAR MAP sensor on SD and then "fudging" the Injector Constant and VE Tables by approximately 50% so you can run a Supercharger.

The only problem is you lower limits are quite high (20 kpa is really 40 kpa) and all the "precision" is becomes twice the value than with a 1 BAR MAP.

EG, on my car the minimal change I can make to a VE value is .4 (occasionally .3). This results in a change in the INT (if BLM is locked at 128) of 2. Thus if I am running INTs of 127, the smallest change I can make to the VE will cause it to go to 129. I can never make it hit 128 as I cannot make a change of only .2 to the VE value.

Now if I install a 2 BAR MAP and fudge it, the smallest change of .4 causes me to affect the INT by 4. Thus if I am at 126 INT, the smallest change will cause it to hit 130. I have lost precision.

But, with the minimum value of MAP being changed from 20 to 40 (since the ECM thinks I am getting only half the values that it really is), you have a major problem in trying to get it to idle and deceleration becomes a problem too.

I suspect the same problems will occur with MAF if you "fudge" it and tuning will be a challenge.

(I think you made the right choice on making "Mighty Mouse" go SD).

 

Unfortunately, jet engines AND turbine engines, which I believe you meant, are both a lot more difficult to operate than just adding fuel. That would be nice, though. Someday, microturbines will be everywhere. You heard it here, first...

 

What about the wells SU-145 MAF. It supposedly flows in the 700-800cfm area. I wonder if it will give a larger than 255g/sec signal. What does the ECM do when the engine pulls more air than 255 g/sec, say in a supercharged engine?

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82' Z-28. 327" w/ flat tops. 216/228/112LS. Pocket ported 041 heads 1.94/1.50 SS valves. World Class T-5 from a 91'. Best run? Runs with 2001 vette to 150mph! Soon to be converted over to TPI w/ supercharger.

 

That's just it...it gets maxed out and cannot adjust the Injector Pulse width any more to compensate for the increased air flow.

As I said, the 7730 SD has the same problem with it only have 1 bar MAP and a supercharger; though I am looking at altering the programming to work better (it still won't overcome the precision problem). The one advantage SD does have over the 165 MAF at this point is the SD can hanle larger displacement motors while the large mouse maxes out the MAF like a SC.

 

I think I understand the limits of the maf systembut how then do the turbo regal guys do it? There deffinatley exceeding the 255 limit. Are they "fudging it" as well?
The typhoons amd cyclones use a 2-bar map with a diferrent ecm correct? Are these hard to find? Can they be programmed to run a V8?

Thanks, forced induction somewhere in the future.

Also my buddy has a turbocharged 91chev truck with a 747 I believe. He's running propane to bypass the problems with the ecm. He'd like to upgrade to TPI and run gas. How undrivable is "fudging" the SD design. I don't think you'd have to fudge much considering he doesn't use muchboost ona prettymild engine.

 

Unfortunately the sy/ty ecm tables are currently set up with a redline of 4800, so there's no tunability above that point

 

As Afgun said, they (Regals and SyTys) use different systems. Much like the newer F-bodies and Y-bodies have ecms that support 512 MAFs AND MAP sensors. Again, different system.

You can search on "GN" or "SYTY" on this board and find some interesting posts on these. I think there is even a link or two to some sites dealing with them.

 

Not many engines want or need a timing or AFR change over that speed.

 

On a stock maf'd GN you can peg the MAF at 2,500 rpm (none stock setup)
So you set the fuel and timing so it just runs it's best. Meaning that if your flowing say 500 g/sec, untill you get there you'll be running alot richer then necessary, which on a turbo motor isn't as bad as you might think.

Luckily there is hardware to run LT1 or LS1 MAFs on a GN.

 

Isn't the GN MAF variable frequency, instead of variable resistance/voltage?

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82' Z-28. 327" w/ flat tops. 216/228/112LS. Pocket ported 041 heads 1.94/1.50 SS valves. World Class T-5 from a 91'. Best run? Runs with 2001 vette to 150mph! Soon to be converted over to TPI w/ supercharger.

 

Yes, frquency

What do you mean instead of?.